code: def _RefMergeGrad(op, grad, _):
      return _MergeGrad(op, grad, _)
  
file_path: tensorflow-upstream/tensorflow/python/ops/control_flow_grad.py
imports: from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import indexed_slices
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import sparse_tensor
  from tensorflow.python.framework import tensor
  from tensorflow.python.ops import control_flow_ops
  from tensorflow.python.ops import control_flow_util
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops.control_flow_ops import *
label_desc: Use image node_id 3 for calling a global function with example usage: _RefMergeGrad(op, grad, _) and returns: _MergeGrad